Also on these boards
Montessori-Inspired Spring Themes and Activities at Living Montessori Now.
Montessori-Inspired Fall Activities - links to themed units with LOTS of fall activities for each theme (apples, pumpkins, autumn leaves, squirrel and nut activities, corn, Halloween, and Thanksgiving) as well as Pinterest boards for each theme.
LOTS of ideas for calendar observances and Montessori-inspired themes and activities throughout September.
November Themed Activities for Kids (Calendar-based observances throughout the month along with lots of themed activities)
Montessori Monday – Montessori-Inspired Fall Playdough Activities - Roundup of Montessori-inspired playdough activities for a number of different fall themes
Top 10 Summer Themes with LOTS of ideas for Montessori-inspired activities this summer - activities for preschoolers through early elementary